You can make very low carb flapjacks using desiccated coconut, flax seeds and chia seeds and ground almonds and melted cocoa butter and or extra virgin coconut oil and powdered erythritol for sweetener or you can use the brown sugar style of erythritol. The only ingredient you can't get from Tesco is cocoa butter and you can get that on Amazon.
The proportions of the dry ingredients can be varied according to your taste and the cocoa butter and coconut oil are to 'glue' it all together. If you prefer you can use 100% cocoa dark chocolate instead of the cocoa butter or you can use a mix of cocoa butter and dark chocolate to get a milder chocolate taste.
You can make the flapjacks using the cocoa butter first and then when you've cut them - melt a mixture of 100% chocolate and cocoa butter and/or coconut oil and then coat them.
I use Montezuma absolute black which is 8% carbs per 100g
Basically mix the dry ingredients together and then melt the cocoa butter and/or chocolate along with the coconut oil (in warm weather you may not need to melt the coconut oil) then smoosh it all together and press it down into a container and bung it in the fridge until it hardens. Then cut. Or you can put it in individual molds.
If you are going to coat with melted chocolate etc then it helps to freeze it first so the melted chocolate sticks better.
It may be a bit more crumbly than you are used to but it is better than nothing.
I am a type 2 diabetic so I am not sure how polyols work for Type 1 diabetics maybe someone else can weigh in on this one but the sweeteners may appear to be high in carbs when you look at the nutritional value but the carbs are polyols and while not all polyols are indigestible the ones in these products are and so for me as a type 2 they do not count as they do not impact blood sugar levels as they are 'unavailable' and don't cause sugar spikes. I have no idea how they work with Type 1 people.
I use them and then I am lucky enough to not need any meds at all then because I keep my carb intake low enough and as a type 2 that works fine for me.
Green Origins Organic Cacao Butter 90g : Amazon.co.uk: Grocery
www.amazon.co.uk